Patient-specific instrumentation and method for articular joint repair

ABSTRACT

Patient-specific instrumentation for use when performing articular joint repair is provided. A patient-specific jig is adapted to be positioned over a bone at an articular surface thereof for assisting in preparing the bone surface for reception of a prosthesis. The jig comprises a bone contacting portion adapted to matingly contact a portion of the articular surface of the bone and a cutting slot adapted to receive therein a saw blade for resecting the articular surface of the bone. The cutting slot may be press-fitted into the opening of a cut guide. A patient-specific plate and a patient-specific rotational guide are also provided for guiding a positioning of the prosthesis over the resected surface of the bone. A method for manufacturing the patient-specific jig is further provided.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a non-provisional of U.S. provisionalApplication Ser. No. 61/651,061, filed on May 24, 2012, U.S. ProvisionalPatent Application No. 61/671,990, filed on Jul. 16, 2012, and U.S.Provisional Patent Application No. 61/787,579, filed on Mar. 15, 2013.

FIELD OF THE APPLICATION

The present application relates to patient-specific instrumentation forarticular joint repair.

BACKGROUND OF THE ART

In arthroplasty, a damaged joint, such as a knee joint, is replaced withprosthetic implants. Prior to implantation of the implant, the damagedregion of the joint is typically prepared by treating regions of thebones to provide surfaces that can align with and therefore accommodatethe implant.

Accuracy in the alignment of the implant is important in thearthroplasty procedure. In knee replacement surgery, this entails properalignment of the knee so the centre of the hip, knee and ankle arealigned in a straight line. This in turn ensures faster patientrehabilitation and better knee function. For this purpose, mechanicaljigs, which ensure accurate position and orientation of finishinginstruments used during bone resection, are typically used duringarthroplasty procedures, such as knee replacements. However, suchconventional jigs may lack precision as they may rely on the user'sjudgment to assess proper positioning of the devices. In addition, eachpatient's anatomy being different, proper component sizing may berequired for optimizing the outcome of the surgery. Still, conventionalcomponents only allow patient customization to a certain degree. Assuch, the use of conventional instrumentation can lead to misalignmentand result in instability and potential wear or even premature failureof the prosthetic implants.

There is therefore a need for improved patient-specific instrumentationfor use during articular joint repair procedures.

SUMMARY OF THE APPLICATION

It is therefore an aim of the present invention to provide novelpatient-specific instrumentation and method.

Therefore, in accordance with the present application, there is provideda patient-specific rotational guide for guiding a positioning of a toolon a resected surface of a bone in an articular joint repair procedure,the rotational guide comprising a body comprising a tool attachmentmember adapted to be secured to the tool; and a bone contacting memberhaving a bone contacting surface shaped using patient-specific modelingto conform to a shape of an articular surface of the bone for matinglycontacting the articular surface when the tool is positioned on theresected surface.

Further in accordance with the present application, there is provided apatient-specific jig for preparing an articular surface of a bone in anarticular joint repair procedure, the patient-specific jig comprising atleast one bone contacting member having a mating surface shaped usingpatient-specific modeling to conform to a shape of the articularsurface, the mating surface adapted to matingly contact a portion of thearticular surface; and a cutting guide adjacent the at least one bonecontacting member and adapted to receive therein a saw blade forresecting the articular surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a flow chart of a method for performing bone resection duringarthroplasty using a patient-specific jig in accordance with the presentdisclosure;

FIG. 1b is a flow chart of the step of creating a patient-specific jigof FIG. 1 a;

FIG. 2 is a block diagram of a patient-specific instrumentationcomputer-assisted system for arthroplasty in accordance with the presentdisclosure;

FIG. 3 is a side perspective view of a patient-specific femoral jig on afemur in accordance with the present disclosure;

FIG. 4 is a bottom perspective view of the patient-specific femoral jigon the femur of FIG. 2;

FIG. 5 is a perspective view of a femur showing femoral jig contactingareas in accordance with the present disclosure;

FIG. 6 is a top perspective view of a tibial jig in accordance with theprior art;

FIG. 7 is a perspective view of the tibial jig of FIG. 5;

FIG. 8 is a top perspective view of a patient-specific tibial jig on atibia in accordance with the present disclosure;

FIG. 9 is a front perspective view of a tibia showing tibial jigcontacting areas in accordance with the present disclosure;

FIG. 10a is a bottom perspective view of a patient-specific femoral jigon a femur in accordance with an alternative embodiment of the presentdisclosure;

FIG. 10b is a side view of the femoral jig of FIG. 10 a;

FIG. 11a is a rear perspective view of a patient-specific tibial jig ona tibia in accordance with an alternative embodiment of the presentdisclosure

FIG. 11b is a top view of the tibial jig of FIG. 11 a;

FIG. 11c is a top perspective view of the tibial jig of FIG. 11 a;

FIG. 12 is a front perspective view of a patient-specific tibial platein accordance with the present disclosure;

FIG. 13a is a perspective view of a rotational guide and of a sizingplate coupled to a plate handle in accordance with a first embodiment ofthe present disclosure;

FIG. 13b is a perspective view of the rotational guide of FIG. 13acoupled to the plate handle and sizing plate;

FIG. 13c is a side view of the rotational guide of FIG. 13 b;

FIG. 13d is a perspective view of the rotational guide of FIG. 13c matedwith a bone surface in accordance with a first embodiment of the presentdisclosure;

FIG. 13e is a perspective view of a rotational guide and of a sizingplate in accordance with a second embodiment of the present disclosure;

FIG. 13f is a bottom perspective view of the rotational guide of FIG. 13e;

FIG. 13g is a top perspective view of the rotational guide of FIG. 13ecoupled to the sizing plate;

FIG. 13h is a bottom perspective view of the rotational guide and sizingplate of FIG. 13 g;

FIG. 14a is a top perspective view of a cut slot in accordance with thepresent disclosure;

FIG. 14b is a front view of the cut slot of FIG. 14 a;

FIG. 14c is a perspective view of the cut slot of FIG. 14 a;

FIG. 14d is a perspective view of the cut slot of FIG. 14a inserted intoa cut guide in accordance with the present disclosure;

FIG. 14e is a perspective view of the cut slot of FIG. 14d showingassembly pins in accordance with the present disclosure;

FIG. 14f is a perspective view of the cut slot of FIG. 14e receiving adrop rod adaptor in accordance with the present disclosure; and

FIG. 14g is a front view of the cut slot of FIG. 14d with a close-upview of crush ribs in accordance with the present disclosure.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Referring to FIG. 1a , a method 100 for preparing a bone usingpatient-specific instrumentation (PSI), and more particularlypatient-specific femoral and tibial jigs, prior to performing anarthroplasty procedure, such as knee replacement, will now be described.Although described herein as relating to total knee replacement, itshould be understood that the method 100 is also suitable for partialknee replacement, or other articular joint repair procedures known tothose skilled in the art. It should also be understood that the method100 may be suitable for repairing other articular joints, such as anelbow, shoulder, wrist, or hip.

The first step 102 of the method 100 illustratively comprisespre-operative planning, during which image data of the patient'sanatomy, e.g. the hip, knee, and ankle regions when total kneereplacement is concerned, may be obtained before surgery. The image datamay be obtained from scans generated using Magnetic Resonance Imaging(MRI), Computed Tomography (CT), ultrasound, x-ray technology, opticalcoherence tomography, or the like. Once the images are obtained, acomputer software creates a three dimensional (3D) model of thepatient's damaged knee joint (step 104), which may be sent to a userover a suitable communication network, such as the Internet. The usermay then visualize the 3D model using a computer (not shown) to planbone resection and prosthesis component placement at the damaged jointregion (step 106). The model further enables the user to determine theprosthesis sizing and shape option, e.g. thickness, length, width, orcurvature, best adapted to the patient given the latter's age, weight,gender, and other pertinent information.

Referring to FIG. 1b in addition to FIG. 1a , once bone resection andprosthesis selection and placement have been planned by the user, theuser's computer plan may be used to manufacture patient-specific jigs(step 108). The patient-specific jigs may be manufactured using a jigblank model as a starting point for the machining process (step 112).The jig blank model may be made of any suitable material, including butnot limited to a polymer, a metal, a cross-linked polymer, a ceramic,and an alloy. In this case, a jig blank model of a given size, e.g.small, medium, or large, selected from a library of blanks and adaptedto the anatomy of the patient's damaged joint may be deconstructed.Parts of the blank model may be removed using a Boolean operation tocarve out the desired shape of the patient-specific jigs (step 114). Ajig having a surface conforming to the joint surface to which theprosthesis is designed to mate, and thus precisely-fitting the patient'sanatomy, may then be obtained (step 116).

A rapid prototyping manufacturing process may further be used tomanufacture the patient-specific jigs. In this technique, a computersoftware may section the 3D representations of an object to bemanufactured into a plurality of distinct two-dimensional (2D) layers. A3D printer then fabricates a layer of material for each layer sectionedby the software. The fabricated layers together form a prototype of thedesired object.

During surgery, the thus manufactured jigs may be precisely fitted overthe patient's knee bones, namely the femur and tibia, at the damagedregion of the knee joint for guiding the bone resection (step 110). Inthis manner, customized bone preparation may be performed as previouslyplanned on the computer by the user. Optimal placement of the bestfitting size and shape of the replacement prosthesis may therefore beachieved.

Referring to FIG. 2, a PSI computer-assisted system for arthroplasty isgenerally shown at 120. The system 120 illustratively receives at animagery unit 122 images of the patient's hip, knee, and ankle regionsfrom any appropriate imaging technology, such as MRI or CT. The imagingtechnology apparatus (not shown) may be part of the system 120. The boneimages are then sent to a processor unit 124, which illustrativelycomprises a bone model generator 126, a planning unit 128, and a PSIgenerator 130. The processor unit 124 has a processor to run anapplication that will generate PSI models used to manufacture PSI, suchas a PSI tibial jig 132, a PSI femoral jig 134, a PSI plate 136, and aPSI rotational guide 138 for use during the arthroplasty procedure, aswill be discussed further below. The processor unit 124 may be anyappropriate computer or processing unit. User interfaces, such as amonitor, screen, touch-screen, keyboard, or mouse, may be part of theprocessor unit 124 for the involvement of an operator in the creation ofthe PSI models.

The bone model generator 126 is illustratively used to interpret thebone images received from the imagery unit 122 in order to create a 3Dmodel of the patient's damaged articular joint, e.g. the knee joint. Forthis purpose, input may be provided by an operator via the userinterfaces to ensure proper adequate segmentation between bone andtissue as well as bone and cartilage, thus increasing the accuracy ofthe generated bone model.

The planning unit 128 may then be used to visualize the bone model andto plan bone resection as well as prosthesis component placement at thedamaged joint. The prosthesis size and shape best-suited to thepatient's unique anatomy may also be determined at the planning unit128. According to the generated bone model and pre-operative planning,the PSI generator 130 may produce the PSI models, which in turn may beused to manufacture at least one of the PSI tibial jig 132, the PSIfemoral jig 134, the PSI plate 136, and the PSI rotational guide 138,the latter being adapted to be placed over a resected bone portion forguiding the position or rotation of a prosthesis component thereon. Forthis purpose, patient-specific modeling may be used to design PSI tools,e.g. the PSI tibial jig 132, the PSI femoral jig 134, the PSI plate 136,and the PSI rotational guide 138, such that each PSI tool has a matingsurface that is a replica of or otherwise precisely conforms to asurface of a bone the tool is to be positioned on. In this manner, thePSI tool matingly contacts the bone surface and precisely fits thepatient's anatomy. The PSI models may be in any appropriate format toallow the manufacture of PSI. For instance, the PSI models may beformatted into numerical control (NC) machine files, technical data,visual or digital models, etc.

Referring now to FIG. 3 and FIG. 4, a femoral jig 200 may first be usedto prepare a distal femoral surface prior to attaching a prosthesiscomponent thereon, in most cases with a bone cement. The femoral jig 200illustratively comprises a bone contacting portion 202 adapted to bepositioned on the patient's femur 204 in flush contact with an articularsurface 206 thereof.

The femoral jig 200 illustratively comprises a cut-slot portion 208having a cutting slot 210 formed therein and adapted to receive a sawblade (not shown) used to execute the pre-planned bone cuts. When thefemoral jig 200 is in position over the femur 204 following exposure ofa distal end thereof during surgery, the cut-slot portion 208illustratively extends along the anterior-posterior direction A. In thismanner, when the femoral jig 200 is in place, the slot 210 is positionedadjacent to the trochlear groove 212 at a lower portion of the femur204, which typically mates with an upper portion of the patient's tibia(not shown) at the knee joint. The saw blade may therefore be used toresect the lower portion of the femur 204.

The bone contacting portion 202 of the femoral jig 200 further comprisesa first pair of pegs 214 a and 214 b, which are respectively positionedadjacent to the medial and lateral femoral condyles 216 a and 216 b andextend away from the femur 204 along the cranial-caudal direction B whenthe femoral jig 200 is in place. The pegs 214 a and 214 b each haveelongated guide bores 218 a and 218 b running therethrough and adaptedto receive therein the drill bit of a surgical drill (not shown). Inthis manner, the user may drill elongated holes (not shown) into thefemur 204. The thus machined holes are adapted to receive thereinfixations, such as pins, screws, or the like, to couple the femoral jig200 to the femur 204 prior to resection thereof. Proper alignment of thepegs 214 a and 214 b along the medio-lateral direction C may further beverified using a device, such as a cut guide 220. For this purpose, thecut guide 220 may be positioned adjacent the pegs 214 a and 214 b andproper alignment with features, as in 222 a, 222 b provided on the cutguide 220, may be verified. In particular, the bores 218 a and 218 b maybe used as guides to drill holes in the distal end of the femur 204 forpositioning the cut guide 220 in a pre-planned position. Any cutsrequired to position the prosthesis component in the preplanned positionmay be subsequently performed.

The bone contacting portion 202 of the femoral jig 200 furtherillustratively comprises a second pair of pegs 224 a and 224 b, whichare positioned adjacent the cut-slot portion 208 and extend away fromthe femur 204 along the anterior-posterior direction A when the femoraljig 200 is in place. The pegs 224 a and 224 b each have elongated guidebores (not shown) running therethrough and adapted to receive thereinfixations, such as pins, screws, or the like, to further securely attachthe femoral jig 200 to the femur 204 prior to resection thereof.Fixations are illustratively first inserted into the pegs 224 a and 224b for attaching the femoral jig 200 to the femur 204, followed byinsertion of fixations into the pegs 214 a and 214 b for furtherstabilizing the femoral jig 200 in place.

Once the femoral jig 200 has been secured and stabilized, the fixationsinserted into the pegs 214 a and 214 b may be removed to enableresection of the distal end of the femur 204. After the femur 204 hasbeen resected, fixations may be inserted back into the pegs 214 a and214 b for attaching a standard cutting block (not shown) to the resectedbone. In this manner, additional cuts, e.g. remaining ones of the fivefemoral cuts to be performed during total knee arthroplasty, may beeffected on the femur 204.

As can be seen from FIG. 3 and FIG. 5, the use of the femoral jig 200advantageously enables the user to have an improved lateral view of thefemur 204, in addition to having a clear view of the trochlear groove212. Indeed, a distal clearance (reference 211 a in FIG. 4) isillustratively formed in the bone contacting portion 202 in the areabetween the cut-slot portion 208 and the pegs 214 a and 214 b. Theclearance 211 a may be shaped and sized to conform to a shape and sizeof the trochlear groove 212. A lower surface 213 of the bone contactingportion 202 may also be shaped so as to contact a reduced surface of thefemur 204. In particular, the shape of the lower surface 213illustratively defines a medial clearance 211 b and a lateral clearance(not shown). The medial clearance 211 b and the lateral clearanceprovide viewing spaces that enable a user to evaluate the degree ofcontact between the femoral jig 200 and the distal surface of the medialand lateral femoral condyles 216 a and 216 b. The distal clearance 211 asimilarly enables to evaluate contact over the surface on the anteriorpart (not shown) of the condyles 216 a and 216 b. As seen in FIG. 5,when the femoral jig 200 is in position, the bone contacting portion 202illustratively makes contact with the femur 204 at a medial femoralcondyle contact area 226 a, a lateral femoral condyle contact area 226b, and an anterior surface contact area 228. The femoral condyle contactareas 226 a and 226 b are illustratively positioned on the distal partof the medial and lateral femoral condyles 216 a and 216 b,respectively, while the anterior surface contact area 228 is positionedon the anterior part of the condyles 216 a and 216 b. In one embodiment,the anterior surface contact area 228 is defined by tabs (not shown)provided on the femoral jig 200 and extending over the flank of thelateral femoral condyle 216 b and over the medial side (not shown) ofthe femur 204 accessible during the surgical procedure. The contactareas 226 a, 226 b, and 228 are illustratively sized so as to beproportional to the size of the femur 204. Visibility of the trochleargroove 212 further ensures that the femoral jig 200 is properlypositioned on the femur 204.

The areas of contact between the femoral jig 200 and the femur 204 mayvary from one patient to the next and are illustratively proportional tobone size. Still, the femoral jig 200 is illustratively designed suchthat, when the femoral jig 200 is in place, no contact is made withareas of the femur 204 where cartilage or soft tissues and osteophyteformation resulting from osteoarthritis may be present. For instance, inthe embodiment illustrated in FIG. 5, the contact areas 226 a and 226 bare located on the articular surface of the femur 204 and avoid themedial and lateral margins (not shown) where osteophytes may be present.This in turn optimizes the precision of the arthroplasty procedure andimproves an outcome thereof. Indeed, it is desirable for the femoral jig200 to make contact with as few areas of the exposed femur 204 aspossible so as to reduce the inaccuracies in the surgical cuts to beeffected.

Referring now to FIG. 6 and FIG. 7, a prior art tibial jig 300 will nowbe described. The tibial jig 300 is adapted to be precisely fit on anarticular surface 302 of the patient's tibia 304. The tibial jig 300illustratively comprises a tibia contacting portion 306 and a pair ofattachment arms 308 a and 308 b each having respectively formed at anend portion thereof plateau contacting portions 310 a and 310 b. Whenthe tibial jig 300 is placed over the tibia 304 following exposure of aproximal end thereof, the tibia contacting portion 306 is adapted tocontact the tibia 304. The attachment arms 308 a and 308 b then extendaway from the tibia 304 along the anterior-posterior direction A withthe plateau contacting portion 310 a making contact with the articularsurface of the medial tibial plateau 312 a and the plateau contactingportion 310 b making contact with the articular surface of the lateraltibial plateau 312 b.

The tibial jig 300 further comprises a cut-slot portion 314 having aslot 316 adapted to receive therein a saw blade 318 used by the user toexecute the pre-planned bone cuts. When the tibial jig 300 is in placeon the tibia 304, the cut-slot portion 314 is positioned adjacent anupper portion of the tibia 304, which typically mates with a lowerportion of the femur 204 at the knee joint. In this position, the slot316 extends along the transverse plane and the saw blade 318 may beinserted through the slot 316 to resect the upper portion of the tibia304. The resected surface of the tibia 304 is in most casesperpendicular to the shaft axis Y of the tibia 304 in the coronal plane.The slot 316 may further be machined into the cut-slot portion 314 so asto enable proper reach of the saw blade 318 during the bone resection.

The pair of attachment arms 308 a and 308 b may respectively comprisepegs 320 a and 320 b, which extend away from the tibia 304 along thecranial-caudal direction B. The pegs 320 a and 320 b each have elongatedguide bores 322 a and 322 b running therethrough and adapted to receivetherein a surgical drill bit (not shown) used to drill elongated holesinto the tibia 304. The thus machined holes are then mated with holesprovided in a provisional tibial sizing plate 324 used to determine theproper size of a prosthetic tibial tray (not shown). The holes in thesizing plate 324 are adapted to receive therein fixations, such as pins,screws, or the like, to securely attach the sizing plate 324 to theresected portion of the tibia 304. For this purpose, the elongated guidebores 322 a and 322 b are spaced and sized to match the spacing and sizeof bores 326 a and 326 b machined into the sizing plate 324. The bores322 a and 322 b thus aid in setting the position and rotation of thesizing plate 324 on the resected portion of the tibia 304. With theproper sizing plate 324 selected and held in place, the proximal tibiacan be further drilled and/or broached to accommodate supportingcomponents, such as stems, of the prosthetic tibial tray.

A second pair of pegs 328 a and 328 b illustratively project from thetibia contacting portion 306 and extend away from the tibia 304 alongthe anterior-posterior direction A when the tibial jig 300 is in place.The pegs 328 a and 328 b each have elongated guide bores (not shown)running therethrough and adapted to receive therein a device, such as adrop rod (not shown), for confirming, subsequent to the tibial cut, thatproper rotation and alignment of the cut relative to the overall tibialshaft axis Y have been achieved using devices, such as traditionaltibial component sizing jigs and rotational jigs.

Referring to FIG. 8 and FIG. 9, a tibial jig 400 in accordance with anillustrative embodiment will now be described. The tibial jig 400illustratively comprises a pair of attachment arms 402 a and 402 b eachhaving a surface contacting portion (not shown) so that the arms 402 a,402 b may respectively make contact with the articular surfaces 404 aand 404 b of the medial tibial plateau 312 a and of the lateral tibialplateau 312 b. The slope of the tibial intercondylar eminence 405 mayfurther be used to lock the medio-lateral position as well as therotation of the tibial jig 400. In particular, when the tibial jig 400is in place, the attachment arms 402 a and 402 b may contact the sidesof the intercondular eminence 405, thereby providing stability to thetibial jig 400.

The tibial jig 400 further comprises a cut-slot portion 406 having aslot 408 adapted to receive therein a saw blade (not shown) used toperform resection of the tibia 304. A tibia contacting portion (notshown) is further provided adjacent the cut-slot portion 406 for makingcontact with the tibia 304 on a region 410 of the medial and lateraltibial plateaus 312 a and 312 b adjacent the tibial tuberosity 411. Whenthe tibial jig 400 is in position on the tibia 304, the cut-slot portion406 is illustratively adjacent an upper portion of the tibia 304 withthe slot 400 being parallel to the transverse plane. At least one lineindicator 412 may further be provided on the cut-slot portion 406adjacent the attachment arm 402 a. The line indicator 412 may be locateon the jig 400 using patient-specific modeling. Alignment of theindicator 412 with the tibial tuberosity 411 may be used to confirm thatthe tibial jig 400 is positioned at a desired rotational angle relativeto the tibia 304. In one embodiment, a first and second indicator as in412 may be respectively provided on the anterior and distal sidescut-slot portion 406 to indicate alignment with the anterior-posteriordirection A. A cut slot plane indicator (not shown) may also be providedon the medial side of the cut-slot portion 406 to indicate alignmentwith the plane along which the pre-planned bone cuts are to beperformed.

Although the areas of contact between the tibial jig 400 and the tibia304 may vary from one patient to the next, a lower surface (not shown)of the attachment arms 402 a and 402 b is illustratively sized and/orshaped such that no mating of the tibial jig 400 is made on an area 413of the tibia 304 where meniscus may be present, thus avoiding any softtissues remaining on the tibia 304 following exposure thereof. Forinstance, the arms 402 a, 402 b may be provided with varus-valgusshapes. Also, the tibia contacting portion is illustratively sizedand/or shaped so as to avoid possible osteophytes that may be present onthe anterior proximal ridge (not shown) of the tibia 304.

The tibia contacting portion illustratively has formed therein a pair ofpegs 414 a and 414 b, which project away from the tibia contactingportion along the anterior-posterior direction A when the tibial jig 400is in place. Elongated guide bores (not shown) may be machined into thepegs 414 a and 414 b for receiving fixations used to secure the tibialjig 400 to the tibia 304. If, subsequent to resection of the tibia 304using the saw blade, it is determined that an insufficient amount ofbone has been resected, a standard cutting block (not shown) may besecured to the pegs 414 a and 414 b for performing additional bone cuts.A clearance (not shown) having a shape and size conforming to the shapeand size of the area 413 may further be formed in the tibia contactingportion to ensure that no contact is made with the area 413 of the tibia304.

FIGS. 10a to 10b and FIGS. 11a to 11c illustrate alternate embodimentsof the femoral jig 200 and of the tibial jig 400. FIG. 10a and FIG. 10billustrate an alternate embodiment 500 of the femoral jig 200 shown inFIGS. 3 and 4. In this embodiment, the femoral jig 500 comprises a bonecontacting portion 502 adapted to be positioned on the patient's femur204 in flush contact with an articular surface 206 thereof, as producedby patient-specific fabrication. The bone contacting portion 502 furthercomprises a first pair of pegs 504 a and 504 b, which are respectivelypositioned adjacent to the medial and lateral femoral condyles (notshown) and extend away from the femur 204 along the cranial-caudaldirection (reference B in FIG. 3) when the femoral jig 500 is in place.The pegs 504 a and 504 b each have elongated guide bores (not shown)running therethrough and adapted to receive therein the drill bit of asurgical drill (not shown).

The bone contacting portion 502 also comprises a second pair of pegs 506a and 506 b, which extend away from the femur 204 along theanterior-posterior direction (reference A in FIG. 3) when the femoraljig 500 is in place. The pegs 506 a and 506 b each have elongated guidebores (not shown) running therethrough and adapted to receive thereinfixations, such as pins, screws, or the like, to further securely attachthe femoral jig 500 to the femur 204 prior to resection thereof.

A clearance 508 may be formed in the bone contacting portion 502 in anarea between the pegs 506 a and 506 b and the pegs 504 a and 504 b. Alower surface 510 of the bone contacting portion 502 may also be shapedso as to contact a reduced surface of the femur 204.

The femoral jig 500 further comprises a line indicator 511 used toindicate the desired location of the bone cut to be performed on thefemur 204. The femoral jig 500 may further comprise a mechanical axispointer 512 provided in between the pegs 504 a and 504 b. The pointer512 illustratively provides an indication as to whether the femoral jig500 is properly positioned on the femur 204. In particular, properpositioning is achieved if the pointer 512 points towards the femur'smechanical axis (not shown), as defined during the pre-operativeplanning phase. A pair of transepicondylar line indicators 514 a and 514b may further be provided on the bone contacting portion 502 adjacentthe pegs 504 a and 504 b, respectively. The indicators 514 a and 514 billustratively protrude away from the bone contacting portion 502 toalign with the lateral and medial epicondyles (not shown).

FIG. 11a and FIG. 11b illustrate an alternate embodiment 600 of thetibial jig 400 shown in FIG. 8. In this embodiment, the tibial jig 600comprises a pair of attachment arms 602 a and 602 b each having asurface contacting portion (not shown) so that the arms 602 a, 602 b mayrespectively make contact with the articular surfaces (not shown) of themedial tibial plateau 312 a and of the lateral tibial plateau 312 b. Atibia contacting portion 604 is positioned adjacent an upper portion ofthe tibia 304 and comprises elongated guide bores 606 a and 606 badapted to receive fixations for securing the tibial jig 600 to thetibia 304. A line indicator 608 may further be provided on the tibialjig 600 adjacent the tibia contacting portion 604. Proper positioning ofthe tibial jig 600 relative to the tibia 304 may be confirmed byalignment of the indicator 608 with the tibial tuberosity (not shown).Patient-specific modeling may be used to determine the position of theindicators 511, 514 a, 514 b, and the pointer 512 on the femoral jig 500as well as the position of the indicator 608 on the tibial jig 600.

Use of the femoral jigs 200, 500 and the tibial jigs 400, 600advantageously decreases errors and enables more precise prosthesisplacement compared to traditional mechanical jigs. In addition, fewerinstruments need to be sterilized for use during the surgical procedure.For instance, the use of patient-specific jigs as in 200, 400, 500, or600 precludes the need for inserting rods through the intramedullarycanal of the bone during the arthroplasty procedure. This in turnreduces the risk of perioperative fat embolism syndrome. Moreover, theuse of patient-specific jigs as in 200, 400, 500, or 600 further allowsfor smaller incisions to be made in the patient's body, thusfacilitating completion of minimally invasive surgery and allowing theprosthesis to more quickly restore the patient's joint to a generallypre-deteriorated state.

Referring now to FIG. 12, a patient-specific plate 700 may be placedover the resected portion of the tibia 304 for guiding the positionand/or rotation of the sizing plate as in 324 over the resected bonearea. For this purpose, a contour 702 of the plate 700 may be designedso as to closely follow a contour of the tibial cut. Apertures as in 704a and 704 b may further be machined into the plate 700 for guiding theuser as to where in the tibia 304 holes should be drilled so as toreceive fixations of the sizing plate 324, thereby attaching the latterto the tibia 304.

In order to ensure a proper fit of the tibial tray (not shown) on theresected portion of the tibia 304, and accordingly a proper positioningof the prosthesis, an outline or contour 706 of the tibial tray may beetched or otherwise delineated onto an upper surface 708 of the plate700. Such a contour 706 may be obtained as a result of the user'spre-operative planning, during which the size and shape of theprosthesis best-suited to the patient's anatomy has been selected. Inaddition, a first axis 710 substantially parallel to theanterior-posterior direction A and a second axis 712 substantiallyparallel to the medio-lateral direction C may be machined on the surface708 of the plate 700. In this manner, while placing the tibial tray onthe resected portion of the tibia 304, a user may verify a properalignment thereof relative to the axes 710 and 712, thereby ensuringproper positioning of the prosthesis. It should be understood thatadditional alignment features as well as other indications, such as thesize and model of the prosthesis component, may also be shown on thesurface 708.

Referring to FIGS. 13a to 13d , a patient-specific rotational guide 800may be used as an alternative to the patient-specific plate 700 toensure proper positioning and rotation of the sizing plate 324 on theresected portion of the tibia (not shown). The rotational guide 800illustratively comprises a tray attachment member 802 for coupling therotational guide 800 to the sizing plate 324. The rotational guide 800may further comprise a bone contacting member 804 for contacting a bonethe sizing plate 324 is to be mated with, the bone contacting member 804being produced by patient-specific fabrication using bone imaging.Although a tibial sizing plate 324 has been shown for illustrativepurposes, it should be understood that the rotational guide 800 may beadapted for use on a bone other than the tibia, for example on thedistal portion of a femur (not shown). It should also be understood thatthe rotational guide 800 may be used with a variety of jig types as wellas for repair of various articular joints other than the knee.

The tray attachment member 802 may be coupled to the sizing plate 324using suitable attachment means (not shown). For instance, the trayattachment member 802 may be clipped to a plate handle 806 coupled tothe sizing plate 324. It should be understood that other means ofsecuring the tray attachment member 802 of the rotational guide 800 tothe sizing plate 324 may apply.

As shown in FIG. 13c and FIG. 13d , the bone contacting member 804 maycomprise a PSI bone contacting surface 808 adapted to mate with acorresponding bone surface 810 of the bone the sizing plate 324 is to bepositioned on. The bone contacting member 804 is designed so that thebone contacting surface 808 precisely matches a geometry of the bonesurface 810. For this purpose, the bone contacting member 804, and moreparticularly the bone contacting surface 808, may be manufactured fromimage data of the patient's anatomy obtained during pre-operativeplanning, as discussed above. In this manner, accurate positioning ofthe sizing plate 324 relative to the bone surface 810 may be achieved.

Referring to FIGS. 13e to 13h , a patient-specific rotational guide 812in accordance with another embodiment will now be described. Therotational guide 812 comprises a tool attachment member 814 configuredto secure the rotational guide 812 to a tool, such as the bone sizingplate 324. The rotational guide 812 further comprises a bone attachmentmember 816 having a mating surface (not shown) configured to contact abone (not shown) the tool is mated with. The mating surface isillustratively shaped so as to conform to a shape of the bone surfacethe bone attachment member 816 is mated with.

In one embodiment, the tool attachment member 814 has a contour (notshown) conforming to the perimeter (not shown) of the tool. The toolattachment member 814 further has a lower surface 818 adapted to matewith the tool. For this purpose, an inner contour 820 of the lowersurface 818 is configured so as to conform to a shape of the tool. Inthis manner, the rotational guide 812 can be retained in positionrelative to the tool when the rotational guide 812 is secured thereto.The lower surface 818 is further provided with attachment means 822,such as clipping means, that enable attachment of the rotational guide812 to the tool. In one embodiment, the attachment means 822 comprise afirst and a second clipping means that allow the rotational guide 812 tobe clipped to the tool. It should be understood that any other suitableattachment means may be provided.

An upper surface 824 of the rotational guide 812 is illustrativelyprovided with one or more alignment elements as in 826 a, 826 b, 826 c,826 d, and 826 e used for confirming the pre-operative planningintra-operatively. The alignment elements as in 826 a, 826 b, 826 c, 826d, and 826 e may further be used for guiding the positioning of the toolon the resected bone surface. In particular, the alignment element 826 amay be an anterior-posterior line formed on the upper surface 824 andindicative of an anterior-posterior direction of the bone. The alignmentelement 826 b may be an medio-lateral line formed on the upper surface824 and indicative of a medio-lateral direction of the bone. Thealignment element 826 c may be indicative of a direction of themechanical axis of the bone. It should be understood that otheranatomical directions may apply. The alignment elements as in 826 d maycomprise openings adapted to cooperate with apertures as in 828 formedin the tool, e.g. the bone sizing plate 324. In particular, when therotational guide 812 is coupled to the plate 324, the alignment elements826 d may be aligned with the apertures 828 to enable fixations (notshown) to be received in the apertures 828 for securing the plate 324 onthe resected surface. The alignment elements 826 e may comprise cutoutsformed in the tool attachment member 814 and adapted to cooperate withapertures as in 830 of the tool, e.g. the bone sizing plate 324. Whenrotational guide 812 is coupled to the plate 324, the alignment elements826 e may also be aligned with the apertures 830 to enable fixations,such as a screws or the like, to be received in the apertures 830.

FIG. 14a , FIG. 14b , and FIG. 14c show and illustrative embodiment of acut slot 900 for use with at least one of the above-mentioned tibial andfemoral jigs. It should be understood that the tibial and femoral jigsmay or may not comprise such a cut slot 900 and that the cut slot 900may be used with non PSI tools. In addition, the cut slot 900 may beprovided as a disposable tool for use with disposable instruments, suchas disposable cut guides.

The cut slot 900 illustratively comprises a first member 902 and asecond member 904 each comprising opposite ends as in 906 ₁, 906 ₂. Eachone of the members, e.g. member 902, is provided at the ends thereof,e.g. ends 906 ₁, with an attachment means, e.g. attachment means 908 ₁,adapted to cooperate with the corresponding attachment means, e.g.attachment means 908 ₂, provided at the ends, e.g. ends 906 ₂, of theother member, e.g. member 904. When so coupled to one another, the firstand second members 902, 904 define therebetween a spacing 910 adapted toreceive therein a saw blade (not shown) used to execute pre-planned bonecuts. In the illustrated embodiment, the attachments means 908 ₁, 908 ₂are adapted to be snap-fitted together. It should be understood thatother attachment means configurations may also apply. It should also beunderstood that the attachment means 908 ₁, 908 ₂ may be provided at asingle one of the ends 906 ₁, 906 ₂ of each member 902, 904 rather thanat both ends 906 ₁, 906 ₂ thereof.

The cut slot 900 is illustratively metallic and the members 902, 904 maybe made of a stamped sheet of metal. It should be understood that avariety of manufacturing processes may be used for the cut slot 900. Forexample, the members 902, 904 may be machined, formed, or the like.Still, regardless of the manufacturing process used, it is desirable forthe cut slot 900 to have a substantially constant width along a lengththereof.

Referring now to FIG. 14d , FIG. 14e , and FIG. 14f , the cut slot 900may be inserted into a housing 912, such as a cut guide housing. Thehousing 912 may be made of plastic or any other suitable material. Thecut slot 900 may be press-fitted into an elongate opening 913 machinedinto the housing 912. For this purpose, the first and second members(references 902, 904 of FIG. 14a ) may be shaped to fit the size of theopening 913. A lip 914 may further be formed in each one of the firstand second members 902, 904 so as to guide, and accordingly facilitate,the insertion of the saw blade into the spacing (reference 910 in FIG.14b ). Assembly pins 915 may then be used to retain the cut slot 900within the housing 912. The housing 912 may further comprise a pluralityof apertures as in 916 for receiving therein bushings 917 (see FIG. 14f) as well as a receptor 918 for a drop rod adaptor 919 (see FIG. 14f ).In one embodiment, the bushings 917 are press-fitted into plastic. Thebushings may be adapted to accommodate the drill bit of the surgicaldrill guide (not shown) and may be used to prevent residual plasticshavings or other debris resulting from the drilling process. Thebushings 917 may also be used to secure the cut slot 900 on the boneduring cutting. In particular, a locking bushing (not shown) may beprovided to stabilize the cut slot 900, and accordingly the tibial orfemoral jig the cut slot 900 is coupled to, during the cuttingprocedure. Accurate positioning of the cut slot 900 relative to the bonemay then be achieved.

As seen in FIG. 14f , the drop rod adaptor 919 may be aligned with twoanterior medial bushings 917 for accurately positioning the drop rodadaptor 919 in varus-valgus as well as ensuring proper rotation of thedrop rod adaptor 919 relative to the cut slot 900. The drop rod adaptor919 may be further stabilized by a ball plunger (not shown) providedthereon. When the drop rod adaptor 919 is inserted into the receptor918, the ball plunger may indeed be retained within an aperture (notshown) formed in the receptor 918. The drop rod 919 may further beprovided with apertures adapted to cooperate with the bushings 917 forreceiving pins as in 921. Pinning can then be performed while the dropadaptor 919 is in place relative to the cut slot 900.

Referring to FIG. 14g , in order to provide accuracy and stability tothe positioning of the cut slot 900 relative to the housing 912, thelatter illustratively has formed therein a pair of inferior crush ribs920 a and a pair of lateral crush ribs 920 b. It should be understoodthat any other suitable number of crush ribs 920 a, 920 b may be used.The crush ribs 920 a and 920 b ensure that the cut slot 900 is stable aswell as account for tolerance variations between the metallic cut slot900 and the plastic housing 912.

The inferior crush ribs 920 a are illustratively positioned adjacent alower surface (not shown) of the second member 904. The lateral crushribs 920 b are respectively positioned adjacent the edge (reference 906₁ in FIG. 14a ) of the first member 902 and the edge (reference 906 ₂ inFIG. 14b ) of the second member 902. Other suitable configurations mayapply. The crush ribs 920 a and 920 b may be made of resilient or othersuitable material, such as plastic, so as to allow the cut slot 900 tobe press-fitted within the housing 912. In particular, each crush rib920 a or 920 b illustratively comprises a base portion (not shown)secured to the housing 912 and a deformable portion (not shown)extending away from the base portion and into the opening (reference 913in FIG. 14d ) formed in the housing 912. When the cut slot 900 isinserted into the opening 913, the cut slot 900 comes into contact withthe deformable portion of the crush ribs 920 a and 920 b. The deformableportion is then crushed, bent, or otherwise deformed or deflected as aresult of the pressure exerted thereon by the cut slot 900 duringinsertion. As a result, the cut slot 900 is then securely retainedwithin the opening 913.

The embodiments of the invention described above are intended to beexemplary. Those skilled in the art will therefore appreciate that theforegoing description is illustrative only, and that various alternateconfigurations and modifications can be devised without departing fromthe spirit of the present invention. Accordingly, the present inventionis intended to embrace all such alternate configurations, modificationsand variances which fall within the scope of the appended claims.

The invention claimed is:
 1. An assembly of a tool and of apatient-specific rotational guide for guiding a positioning of the toolon a planar resected surface of a bone in an articular joint repairprocedure, the assembly comprising: the tool having a planned positionrelative to the planar resected surface of the bone and having a plateportion with a flat surface adapted to be placed against the planarresected surface such that the plate portion with the flat surface movesalong the planar resected surface; the rotational guide including abody, a tool attachment member attached to the tool, and a bonecontacting member having a bone contacting surface adapted to contact abone and shaped using patient-specific modeling to conform to a shape ofa bone surface adjacent to the planar resected surface, apatient-specific arrangement between the rotational guide, the tool andthe bone corresponding to a pre-operative planning defined by a matingcontact between said bone surface and the bone contacting surface whenthe tool is positioned in the planned position on the planar resectedsurface.
 2. The assembly of claim 1, wherein the tool attachment memberhas an inner contour conforming to a shape of the tool for retaining thetool attachment member in position relative to the tool when the toolattachment member is secured to the tool.
 3. The patient-specificrotational guide of claim 1, wherein the tool attachment member has anouter contour conforming to a perimeter of the tool.
 4. The assembly ofclaim 1, wherein the tool attachment member comprises at least oneattachment means securing the tool attachment member to the tool.
 5. Thepatient-specific rotational guide of claim 1, wherein the body comprisesat least one alignment element located on the body usingpatient-specific modeling for guiding the positioning of the tool on theresected surface of the bone.
 6. The patient-specific rotational guideof claim 5, wherein the at least one alignment element is indicative ofat least one anatomic direction of the bone.
 7. The patient-specificrotational guide of claim 5, wherein the tool has formed therein atleast one aperture and the at least one alignment element comprises atleast one opening adapted to cooperate with the at least one aperturewhen the tool attachment member is secured to the tool, the cooperatingat least one aperture and at least one opening adapted to receivetherein at least one fixation for securing the tool to the resectedsurface.
 8. A system of a patient-specific jig and patient-specificmodel for preparing an articular surface of a bone in an articular jointrepair procedure, the system comprising: the patient-specific modelincluding a geometry of the patient-specific jig relative to the boneand including a bone contacting member and a cutting guide correspondingto a planned mating contact between the patient-specific jig and to aplanned planar resected surface aligned with the cutting guide; thepatient specific jig including at least one bone contacting memberadapted to contact a bone and having at least two mating surfaces shapedusing patient-specific modeling to conform to a shape of the articularsurface, the mating surfaces adapted to matingly contact a portion ofthe articular surface, and a cutting guide adjacent to the at least onebone contacting member and having an elongated slot defined by a pair ofparallel surfaces defining an aperture adapted to receive therein a sawblade for resecting the articular surface into a resected surfaceparallel to the aperture, the elongated slot being in a portion of thebone contacting member between the two mating surfaces.
 9. The system ofclaim 8, wherein the at least one bone contacting member has formedtherein at least one clearance shaped to conform to a shape of at leastone selected area of the articular surface for preventing contactbetween the mating surfaces and the at least one selected area.
 10. Thesystem of claim 9, wherein the at least one clearance is shaped toprevent contact between the mating surfaces and at least one ofcartilage, soft tissue, osteophytes, and menisci.
 11. Thepatient-specific jig of claim 10, wherein the mating surface of the atleast one bone contacting member is adapted to matingly contact a distalsurface of a lateral femoral condyle, a distal surface of a medialfemoral condyle, an anterior surface of the lateral femoral condyle, andan anterior surface of the medial femoral condyle.
 12. Thepatient-specific jig of claim 10, wherein the mating surface of the atleast one bone contacting member is adapted to matingly contact aproximal surface of a lateral tibial plateau, a proximal surface of amedial tibial plateau, and an anterior proximal tibial surface.
 13. Thesystem of claim 10, wherein at least one of the mating surfaces of theat least one bone contacting member has a first size proportional to asecond size of the bone.
 14. The system of claim 8, wherein the at leastone bone contacting member comprises at least one alignment elementdefined on the at least one bone contacting member in pre-operativeplanning using patient-specific modeling for guiding a positioning ofthe jig on the resected surface of the bone.
 15. The system of claim 14,wherein the at least one alignment element is physically aligned with atleast one anatomical direction of the bone.
 16. The system of claim 15,wherein the at least one alignment element is aligned with at least oneof an anterior-posterior direction of the bone and a mechanical axis ofthe bone obtained in pre-operative planning.
 17. The system of claim 14,wherein the at least one alignment element is indicative of a planealong which the articular surface is to be resected based onpre-operative planning.
 18. The system of claim 8, wherein the cuttingguide comprises an opening for receiving therein an insert, the insertcomprising a first member and a second member coupled to the firstmember and spaced therefrom for defining the aperture adapted to receivetherein the saw blade.
 19. The system of claim 8, wherein drill boresopen into each of the mating surfaces, the elongated slot being betweenthe drill bores of the mating surfaces.
 20. The system of claim 8,wherein the elongated slot opens into at least one of the matingsurfaces.